Ship propulsion



Sept. 30 1924.

L. RASK SHIP PRPULSIQN' Filed June 14 1923 2 Sheets-Sheet 1 7 33 Inventor? 5 5 Lou/L5 IPaS/r,

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L. RASK I SHIP PROPULSION Filed June 14, 192-3 2 Sheets-Sheau 2 InQent'ow: Louis Rasfi b Magi:

ms Attorney.

Patented Sept. 30, 1924.

LOUIS RASK, F SCHENECTADY, NEW YORK, ASSIGNOR COMPANY, A CORPORATION OF NEW TO GENERAL ELECTRIC YORK.

snir PROPULSION.

Application filed June 14, 1923. Serial No. 645,441.

To all whom it may concern:

Be it known that I, LOUIS RAsK, a citizen of the United States, residing in Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Ship Propulsion, of which the following is a specification.

My invention relates to ship propulsion, and especially to systems of electric ship propulsion in which variable speed propeller motors are supplied with current from alternating current generators driven by steam turbines or other suitable prime,

movers.

An object of my invention is to provide an improved arrangement in which a number of generators are arranged to supply current to a greater number of motors or motor units, each arranged to drive a difier- 0 ent propeller shaft. More particularly an object of my invention is to provide an improved arrangement for, a triple screw ship in which two generators are arranged to supply three motors each arranged to drive one of the ships propellers.

Further objects of my invention are to provide a system of the class described whereby the power for operating the ship may be generated controlled and utilized in a simple, reliable and efficient manner, to provide a triple screw propulsion system in which the middle propeller motor will automatically operate at the desired speed for difl'erent speeds of the outboard propeller motors without s ecial care on the part of the operator, an to provide an arran ement which permits of bringing the mid 1e motor up to speed without the use of external resistors.

In heavy storms it is desirable to be able to drive the outboard propellers at different speeds in order to head the ship into the wind, and it is desirable that the middle propeller run at an intermediate speed during the o erations. In accordance with my invention, each outboard propeller in this triple screw equipment is driven by a single fed induction motor provided with pole ohangin means so that said motors are adapte for operation on a plurality of pole numbers. The middle pro eller is driven by a double fed motor, pre erably adapted for operation on a single pole number, and the connections of the middle propeller motor are controlled by board propeller motors the reversing and pole changing means for the outboard propeller motors in such a manner as to insure the proper connection and operation under all conditions, including both maneuvering and full speed and slow speed operation. Normally the outwill be supplied from independent generators and the rotor and stator of the middle propeller motor will be supplied from the respective generators, but the arrangement is such that when desired all three screws may be driven from a single generator.

My invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the ap pended claims.

Referring now to the drawings, Fig. 1 shows a system of ship propulsion in which my invention has been embodied, Fig. 2 shows a controller interlocking arrangement which may be used to prevent reversal of the motor connections when operating at high speed, and Fig. 3 is a simplified dia- 80 gram of a system similar to that shown by Fig. 1 shows two steam turbines 1 and 2 adapted to drive generators 3 and 4 respectively from which power may be supplied to the single fed induction motors 5 and 6 which are constructed to operate on a plurality of pole numbers, and to the middle motor 7 which is of the double fed type and has its primary and secondary windings arranged for operation on a number of oles twice that of the low pole number 0 the motors 5 and 6. From the generator 3 power may be supplied to the motor 5 through generator switch 8, reverslng 95 switches 9, 10 and 11 controlled by the controller 12, and pole changing switch 13 arranged for operation on a comparatively high number of poles or switch 14 adapted for operation on a lower number of poles. Purely for the purpose of illustration the legend 24 Poles has been placed above the switch 13 and the legend 16 Poles above switch 14 to indicate that the higher number of poles is obtained by switch 13 and the lower number by the switch 14. The switches 13 and 14 may be controlled m' any suitable manner vas b a controller 15 or by cams and a cam sha which also may be used to operate the pole changing switches generator switch 24 and 25 of the motor 6 as will be apparent to those skilled in the art. From the generator 4 power may be supplied to outboard motors 6 through generator switch 19, reversing switches 20, 21 and 22, and either high pole number switch 2 1 or low pole number switch 25. The reversing switches 20, 21 and 22 may be controlled in any obvious manner as by a controller 23 or if desired by a cam shaft which also may be used to. ar'uate the reversing switches 9, 10 and 11 in a well known manner. The pole changing switches 24 and 25 have been shown as actuated through a controller 25 and legends 24 Poles and 16 Poles have been placed above them to indicate their respective functions.

Controlled by the reversing controller 12 is the switch 16 by which the stator winding 17 of the motor 7 may be connected to the generator 3 through the line 18 and the 8. The secondary winding 29 of the motor 7 may be connected to the generator 4:: through the switch 27 the pole changing switch 25, reversing sw1tches 20 and 22, line 28 and generator switch 19 during the high speed ahead operation of the. motor 6, or short-circuited through switch 27 and certain parts oi. the switch 24: during low speed ahead operation of this motor. During reverse operation of the motors 5 and 6 the motor 7 is disconnected from the system due to the fact that the reversing controller 12 which controls the reversing switch 11 and the motor stator switch 16 and the reversing controller 23 which controls the reversing switch 22 and motor rotor switch 27 are in a position to deenergize the operating coils 35 and 36 by which these switches are held in closed position. V7 hen operating the motors 5 and '6 at low speed ahead the stator winding 1'? of the motor 7 is connected to the line 18 through the switch 12 and its rotor winding is connected through switch 27 to certain parts of the switch 24 by which it is short circuited.

As shown in Fig. 2, the controllers 12 and 15 may have their cperatin shafts 31 and 32 respectively mechanica ly interlocked through members 33 and 3 1. Like inter-. locking means may be provided for prevent-- ing movement of the reversing controller 23 when the pole changing controller 26 is in high speed position.

Assuming the outboard motors 5 and 6 each to be arranged for operation on 16 and 2d poles, the stator and rotor windings of themiddle motor are each provided with 32 pole windings as indicated in the drawing and each or these windings are arranged to produce fields rotating in the same direction. 'With the genertator switches 8 and 19 closed and the reversing controllers 12 and 23 set for ahead operation the ship may be started from rest by moving the pole changing controllers 15 and 26 to the low speed or 24: poles position in which the motors 5 and 6 are connected for operation on 24: poles and the middle motor- 7 is driven by the generator 3 as an induction motor with short-circuited secondany at a speed corresponding to the slip of the middle propeller which is not required to supply any torque during low speed operation. To bring the ship up to full speed ahead the pole changing controllers 15 and 26 are moved to high speed position thereby connecting the motors 5 and 6 for operation on 16 poles and connecting the stator winding of the middle motor 7 to the gen erator 3 and its rotor winding to the gen orator 1 for operation at the same speed as that at which the outboard motors 5 and 6 are'operated. Under these conditions the three motors are arranged to exert equal torques and equal amounts of power are supplied by the two generators, each genera tor supplying the power utilized by one outboard motor and by one winding of the middle motor.

In order to reverse the ship the pole changing controllers 15 and 26 must be moved to low speed or 24 pole position. The reversing controllers 12 and 23 may then be moved to reverse position thereby entirely disconnecting the middle motor 7 from the system'and connecting the outboard motors for operation on 24 poles at which speed the maximum reversing torque or the system is available.

Turning of the ship is readily accomplished in well-known manner by driving the turbo-generator sets at difierent speeds since the double fed motor by which the center screw is driven assumes a speed intermediate that 01? the outboard'propellers without any special attention on the part of the operator.

Fig. 3 shows a s stem which is similar to that shown in ig. 1 but difiers therefrom in that switches 31 and 32 are provided for short-circuiting the stator and rotor windings of the motor 7, only one conductor or each three phase lines of the systern has been shown for the purpose of simpliiying the drawing. This arrangement increases the flexibility o1 the system. In case of injury to either the rotor or stator winding it is still possible to operate the motor 7 at the slip speed of the propeller by connecting the sound winding to the source of power and operating the injured winding as a short-circuited seconds My invention may be uti ized in other forms than those in connection with which it has been illustrated and described. Thus the two phase system, for example, may be replaced by any suitable polyphase system, the motors may be provided with any de- Elli , double fed motor, a p uralityof single fed motors, and means for interconnecting said motors with said source whereby at full speed of the ship said motors may be caused to exert e ual torques and at cruising speed said dou'b e fed motor may be driven at a' speed corresponding to the slip of the propeller 2. A system of ship propulsion wherein electric motors are arranged to drive the ships propellers, comprising a propeller arranged to be driven b a double fed motor, a plurality of propel ers each arranged to be driven by a single fed motor a plurality of sources of power, and means for connecting a part of said single fed motors in parallel with the rotor winding of said double fed motor to one of said sources and for connecting another part of said single fed motors in parallel with the stator windin of said double fed motor to another of Said sources.

3., A system of electric ship propulsion wherein electric. motors are arranged to drive the ships propellers, comprising a propeller arranged to be driven by a double fed motor, a plurality of propellers each arranged to be driven in either direction by a different single fed motor constructed for operation on a plurality of pole numbers, a source of power, and means for connecting said motors in parallel to said source when said single fed motors are operating on one pole number in one direction andfor disconnecting said double fed motor from said source when said single fed motors are operated in the reverse direction on another pole number.

4. A system of electric ship propulsion wherein electric motors are arranged to drive the ships propellers, comprising a promotor, a lurality of prope lers each arrangedto e driven in either direction by a difierent single fed mot-or constructed for operation on a plurality of ole numbers, a source of power, and means or connecting said motors in arallel to saidsource when said single fed motors are arranged for ahead operation on one pole number and for short-circuiting one winding of said double fed motor and connecting its other windin to said source in parallel with said single ed motors when said single fed motors are arranged for ahead operation on a lower pole number.

5. A system of electric ship propulsion wherein the propeller motors are arranged to 'be supplied with current from a plurality of alternating current generators, comprising a double fed motor, a plurality of single fed motors, means for controlling the connections of said double fed motor and reversing the phase rotation of said single fed motors, switches for changing the pole number of said single fed motors, and interlocks for locking said means in operative position when said single fed motors are connected for operation at high speed.

6. The method of operating a system of electric ship propulsion wherein an alternating current generator is arranged to supply eurrent to a double fed motor and a plurality of single fed motors which consists in driving all the motors at the same speed when the ship is operating at full speed ahead, driving the double fed motor at a speed corresponding to the slip of the propeller when the ship is operating at cruising speed, and disconnecting said double fed motor from said generator when said ship is driven in the astern direction.

7 A system of ship propulsion wherein electric motors are arranged to drive the ships propellers, comprising a middle propeller arranged to be driven by a double fed motor, two outboard propellers each arranged to be driven by a different single fed motor, a source of power, and means for connecting said motors in parallel to said source.

In witness whereof, I have hereunto set my hand this 13" day of June, 1923.

. v LOUISE-ASK. 

